The present invention relates in general to superconductors and, in particular, to a new and useful apparatus and method of making cable-in-conduit-conductors or CICC""s.
Superconducting cables integrated into a metal jacket can be used as windings of coils which create very strong magnetic fields. At present, two previous methods are known to the inventors for the commercial manufacture of such Cable-In-Conduit-Conductor (CICC). The first method involves conventional cable handling equipment used in conjunction with seam welded tube manufacturing equipment. The second method relies upon pre-manufactured tubing, cable and a die block to produce the final product. Each of these prior art methods will be described in greater detail below.
In the first method, superconducting cable is created in a continuous length coil which is, in turn, loaded in a cable payout machine. A metal jacket material, in coiled strip form, is also provided to act as strip material. The jacket material is positioned directly under the superconducting cable proximate the payout machine. The cable and jacket materials are simultaneously fed into a series of rolls in a tube-forming mill. The forming rolls of the mill bend and roll the strip material around the cable to form an encasing tube. The tube is then subjected to a seam welding process so that the edges of the strip material of the jacket are joined to produce a leak tight tubular product. Additional forming rolls after the welding process reduce the diameter of the tube, forcing the strip material into intimate contact with the superconducting cable. Keeping in mind that the shape of the conductor can aid the winding process of the final coil, further forming processes may be used to form the jacket material into a square, oval, rectangular or other cross section as required by the conductor design specification, and the final CICC product is wrapped onto a storage spool until the coil winding process begins (see below).
A major drawback of this first method involves the welding process required, insofar as the superconducting cable may be damaged during this welding. Consequently, the first method described above typically results in CICC product of lower quality in comparison to other known manufacturing processes.
The second method uses pre-manufactured lengths (typically 20 ft.) of either welded or seamless tubing as the jacket material. The jacket material is stacked vertically in a equilateral triangular rack. Superconducting cable is then provided as a continuous length coil which is pulled through the hollow center of the jacket material. This cable pulling operation is started at the bottom of the rack and progresses upward in a helical fashion through each subsequent layer of tubes until the stringing operation is complete. Removing the first two tube sections from the bottom of the rack begins forming of the CICC. The tubes are slid together and joined by an orbital butt weld (over the cable) to produce a leak tight joint. The tubing is then pulled through a die (or series of dies) to produce the desired final shape. Once formed, the final product is wrapped onto a storage spool.
A significant disadvantage of this second manufacturing process results from its rack assembly. The orientation of the rack can limit the efficiency of the manufacturing operation.
The present invention is drawn to a system for fabricating a cable-in-conduit-conductor. The system has a work surface with superconductor cable distribution means situated on one end of the surface. This distribution means will also serve to guide the cable through a tube placed on the work surface, thereby creating a portion of cable encased within tube. Drum means are located on opposite sides of the work surface, and these serve to assist in bending and redirecting the cable without damaging it. Notably, the cable is bent around the first drum means and returned to across the work surface without pulling the cable through any additional tubes, thereby creating a naked length of cable. In contrast, the second drum means is capable of guiding the naked length of cable into additional tubes on the work surface, thereby creating additional portions of cable encased within tube. Finally, tension means and compression means work together to process the cable encased within tube into a single length of cable-in-conduit conductor (CICC). Additional items, such as collection means for collecting the CICC and/or orbital butt welding apparatus, may also be provided.
The present invention also contemplates a method for creating CICC. Essentially, this method includes pulling a superconductor cable through an appropriate tube situated on a work surface, bending and returning the exposed cable along the work surface, bending and pulling the cable back through a separate tube and finally compressing the cable encased in tube portions to eliminate the exposed lengths of cable while, at the same time, joining each section together. As above, this joining operation may be performed via orbital butt welding, and the pulling and returning operations can be performed numerous times until the desired length of CICC product is produced.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.